Sudden cardiac death (SCD) results in approximately 450,000 deaths each year in the United States alone of older adults. Most fatal SCD events are caused by ventricular arrhythmias (ventricular tachycardia and ventricular fibrillation) in patients both with and without identified structural heart disease. Proposed is a personal ambulatory arrhythmia monitoring and automated alerting device for the many hundreds of thousands of patients in the U.S. known to be susceptible to death from arrhythmia but not deemed at high enough long-term risk for prophylactic therapy with an implantable cardioverter-defibrillator (ICD). Indoor arrhythmia monitoring and alarming devices presently exist that are connected to a land-line phone and call service centers to initiate a response. Unfortunately there exists no equivalent device for patients walking outdoors or in a car where they are at risk for unwitnessed cardiac arrest. The proposed rapid alert device is intended for patient use out of the home, when exercising or travelling alone in a car for example, to automatically detect arrhythmia events, alert locally, call 911, and report a victim's location. PUBLIC HEALTH RELEVANCE: Sudden cardiac death (SCD) results in approximately 450,000 deaths each year in the United States and represents a health problem of epidemic proportions. Currently, beyond ten minutes after victim collapse, the likelihood of complete physical and neurologic recovery with conventional resuscitation is very low and overall survival for arrest victims is less than ten percent. This project proposes to develop wearable technology to automatically identify life-threatening cardiac arrhythmia, alarm locally, call 911, and report the victim's location to enable responders to provide defibrillation therapy as quickly as possible.